During exposure, interference takes place between the incident rays and those reflected by the mirror, with the formation of interference fringes half a wavelength distant from each other.

The plate at each point only sends back to the eye the simple colour imprinted. The other colours are destroyed by interference. The eye thus perceives at each point the constituent colour of the image.

This result is due to a phenomenon of interference which occurs within the sensitive layer.

The series of photographic operations, developing, washing, final drying, takes about quarter of an hour.

The length of exposure (one minute in sunlight) is still too long for the portrait. It was fifteen minutes when I first began my work. Progress may continue.

There lived a Parsee from whose hat the rays of the sun were reflected in more-than-oriental splendour.